Yes, they are linked with an air-line between the two vacuum chambers. In the picture below, my new carbs with factory vacuum chamber covers (and the old air filters) are shown. Below that are my old carbs where I drilled and tapped the vacuum covers for 90degree grease fittings that had the balls and springs removed. I got those old ones free.

Someone had drilled ragged looking holes into the choke towers. I eventually decided to buy new ones as the idle was always rich. Two carbs meant twice the fuel at idle. I had the mixture screws all the way in and it was OK. With the new carbs, the mixture screws wound up about 1/4 turn out.